Adapting wavelet compression to human motion capture clips
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Adapting Wavelet Compression to Human Motion Capture Clips. Philippe Beaudoin 1 Pierre Poulin 1 Michiel van de Panne 2. 1 Universit é de Montréal, LIGUM 2 University of British Columbia, Imager. A need for compression?. Motion capture is very popular

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Adapting Wavelet Compression to Human Motion Capture Clips

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Adapting wavelet compression to human motion capture clips

Adapting Wavelet Compression to Human Motion Capture Clips

Philippe Beaudoin 1Pierre Poulin 1Michiel van de Panne 2

1 Université de Montréal, LIGUM2 University of British Columbia, Imager


A need for compression

A need for compression?

  • Motion capture is very popular

  • Motion capture rapidly produces huge collections of data

  • Escalating cost of the memory hierarchy (ie. Martin Walker talk)

  • Lossy compression

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


What is a good compression

What is a good compression?

  • Depends on the application

  • We aim for:

    • Small cache footprint

    • Access to subset of joint data

    • Accurate foot placement

    • Independent motion clips

  • Best ratio may not be the target

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Which kind of compression

Which kind of compression?

  • Joint correlation

    • 2:1 up to 4:1 (PCA)

  • Joint + temporal coherence

    • Cannot access individual signals

    • 30:1 up to 35:1 [Arikan 06]

  • Temporal coherence alone

    • 35:1 (this work)

    • Access to subset of joint data

    • Low computational requirements

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Preliminary details

Preliminary details…

  • A pose is…

    • Root position (3 signals)

    • Euler angles of joints (59 signals)

  • Motion is sampled at 120 hz

  • No preprocessing or format conversion before compression

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Standard wavelet compression

Standard wavelet compression

  • Cubic interpolating bi-orthogonal wavelet basis [Sweldens 98]

  • Not specially targeted to motion capture

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Standard wavelet compression1

Standard wavelet compression

  • Wavelet transform 62 signals

  • Keep the largest coefficients from all the transformed signals

  • Yield vector wi (1 ≤ i ≤ 62) counting how many coefficients are kept for each signal

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Adapting wavelet compression to human motion capture clips

Vector wi

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Optimized coefficient selection

Optimized coefficient selection

  • wiminimizes RMS error in the DOF

  • Quality depends much more on positional distortion

  • Optimally redistribute coefficients?

    • Too costly!

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Optimized coefficient selection1

Optimized coefficient selection

  • Motion capture data is hierarchical

  • Build vector mi that favors some signals more than others

  • Fixed choice for mi? Bad!

    • Depends on complexity of signals

    • Depends on the poses

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Adapting wavelet compression to human motion capture clips

Start withmi = wi

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Adapting wavelet compression to human motion capture clips

Randomly select i reduce mi

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Adapting wavelet compression to human motion capture clips

Find optimal j increase mj

Repeat…

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Inverse kinematics correction

Inverse kinematics correction

  • Problem: Noticeable sliding feet

  • Change distortion metric?

    • Assumption breaks down, difficult to find a good mi

  • Instead, add positional channels for the feet, use IK

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Inverse kinematics correction1

Inverse kinematics correction

  • Signals encode difference between compressed position and true feet position

  • Wavelet compress these signals independently

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Final details

Final details…

  • Quantize to 16 bits

  • Run-length encode 0s

  • Optionally use lempel-ziv independently on each clip

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Results

Results

  • Tested on 1 sec. to 45 sec. clips

  • Compression ≈ 300 ms/frame

  • Decompression

    ≈ 30 μs/frame(no IK)

    ≈ 300 μs/frame(with IK)

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Video

Video

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Conclusion

Conclusion

  • Tractable coefficient search space adapted to motion capture data

  • Fast decompression

  • Access to subset of joints

  • Independent clips

  • 35:1 compression ratio

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Future work

Future Work

  • Metric for perceived quality in a motion capture animation

  • Explore large-scale redundancies (see our technical report)

  • Level-of-detail streaming

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


Questions

Questions?

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007


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